Another heat treat fail (but getting closer)

[toggy]

I whipped up another blade and did a heat treat. It's 1095 and I got it to non-magnetic. Quick plunge in warm brine and then a hand-straightening. Twas looking good. File slid across the steel without biting. Seemed like a nice, hard blade. I went to polish a small area before tempering and noticed the crack.



I should have known better, but I did have a weak edge on it. I think that may have contributed to the crack.

Perhaps water is just too harsh of a hardening medium?

I am looking at it as a victory because I did in fact harden the steel.

A side question, would you guys start to shape the blade grind pre-heat treating? Should I just rough out the shape and then grind the blade and point?

I don't want to wast a lot of stone and sandpaper shaping hardened steel. OR do you get the blade 90% shaped and then heat treat.

[Doug Lester]

A couple of questions, how far out did you sand the blade before quenching? Where did you get the 1095?

Brine is about as harsh a quenchant as you can use and rough grindng marks are stress risers. I would recommend that you sand out to at least 220 grit.

Unless you got your 1095 from the New Jersey Steel Baron you may be stuck with an agressive quenchant but you could always try something like vegetable oil and see how it does. You also might want to invest in a quenchant made for shallow hardening steel like Parks #50.

Doug

[Ray Rogers]

I agree with Doug, no coarse grind marks in the steel, no square corners, and I'd choose to quench in most any oil before I'd use brine or water. Brine and water work great for hardening 1095 but the failure rate due to cracking is at least 30% when I do it. I now use Tough Quench on 1095 and the steel gets just as hard and never had a blade crack.

But, you also said you quenched in brine and then tried to straighten the blade - that's a sure fire recipe to crack a blade. Never try to straighten a cold blade and by 'cold' I mean anything less than 400 F (which is barely possible) and almost hot enough to start glowing red is much better.

As to grinding, I profile before but do all my bevel grinding after HT but many others prefer to grind before. After avoids a lot of warping issues but will wear your belts faster. Figure one belt of each grit for a blade which is cheap by my estimation. Others like the 90% shaped before HT method but, in the end, I doubt they save as much in belts as they lose in time trying to correct warps and clean up the blade ....

[Doug Lester]

Ray, a quick question. You say you harden before you grind your bevels. Does that include 1095?

Doug

[toggy]

Thanks a ton guys. First some answers:

I got the steel from Admiral

I sanded the bevels using a rough grit. 40 or 80.



I didn't realize that brine was the harshest. I will try warm oil next time. I thought the blade was still hot enough for a little straightening but perhaps it was not. I don't know if the crack came when quenching, straightening or as I started sanding (when I saw it.)

[Ray Rogers]

Doug,

All steels for blades up to 3/16" thick. Over that, which is very rare for me, I might do a partial grind leaving the edge much thicker than normal. Of course, all of this is done after the entire HT is done, cryo, tempering, all done ....

Toggy,

Brine isn't the harshest, plain water is, but brine isn't all that much easier. The crack could have come from simply an 80 grit scratch. Or, from the flexing that might have happened when you sanded the blade. In point of fact, 1095 can easily crack even if you don't put any stress at all on the blade, even just laying on a table by itself unless you get it into the tempering oven ASAP after quenching ....

[toggy]

So quench in oil and straight to the oven. Perhaps the harsh quench is contributing to the bending? Maybe oil would require less straightening.

So do you guys bevel a little before hardening. I also wouldn't want to ruin the hardening by overheating the blade with all that shaping...

[Ray Rogers]

The harsh quench might be aggravating the bending but if the steel warped then it is because there are stresses in the steel. When you grind bevels that can introduce stress into the steel which is one of the main reasons I wait to grind bevels until after the HT is complete. But, you didn't grind if I'm seeing that picture correctly so that means the stress was already in the steel. Perfectly annealed steel shouldn't have that problem but, as has already been pointed out, 1095 from different sources can vary greatly. So, you need to relieve the stress as you do the heat treat - you need to normalize the blade.

Heat the blade up to a little beyond non-mag and then pull it out of the heat and let it cool in still air until you can touch it without blistering your hand (150 F or so). Put it back in the heat and repeat 3 times. If you notice a warp during this process that is the time to do your straightening but be GENTLE - steel that hot bends very easily. After the third cooling proceed with the hardening as usual.

You won't ruin the hardening by grinding as long as you learn the rules (just like anything else, you have to know how). First, use fresh, sharp belts - ceramic is best. Sharp belts don't generate as much heat. Second, grind with your bare hands - no gloves - so you can feel the blade temp. If it burns your fingers it's way too hot so after every one or two passes on the belt dip the blade in a bucket of water. With practice, this process can be done almost as fast as you can grind an annealed blade ....

[Doug Lester]

If the steel is from Admiral you may have to do the water or brine or go to a fast commercial oil formulated for shallow hardening steel. You will really have to watch the stress risers if you are going to use water or brine.

There's another way for you to straighten the blades, actually more then one. One that appeared on this or another board involves clamping the blade to a straight piece of steel. Something thick enough that it won't flex. You could even some broad angle iron. It only need to be long enough to clamp the blade to.

Temper the blade one time an let it cool. Then use steel C-clamps to secure the blade flat against it and repeat the tempering. If you need you can put something like a dime or a penny under the blade to force it to counter bend a little.

Most of all make sure that the blade is really straight before quenching and do not move it side to side in the quenchant. Actually, I don't like to agitate the blade at all.

Doug

[toggy]

So the 1095 from the steel baron is easier to harden? i am considering ording from him the next time.

[Ed Tipton]

Toggy...I think you may be missing a couple of points here. One thing is that 1095 has something of a bad reputation on this forum for being less than dependable in it's characteristics. That is why one of the first questions was "Where did you get it from?" The Steel Baron (Aldo Bruno) is known to be one of the best providers of known good steel. The second thing is that even if you get the steel from Aldo, 1095 is probably not the best choice of steels. This is a steel that is certainly capeable of producing a fine knife, but it is also capeable of giving even experienced knifemakers more than they bargained for in the way of problems.
It is my opinion that you would be well served to consider changing to something like 1080 steel which is known to be much less tempermental and much more forgiving, and still capeable of producing a fine quality knife. It is basically all the benefits without all the hassle.
Using 1080, I complete my profile and bevel grinding to about 90% prior to hardening the steel. I also forge my blades, and take considerable effort to treat both sides of the blade as equally as possible during all phases of the process in an effort to keep all stresses as equal as possible. I quench in commercial quenching oil....not sure which one it is...but rarely have problems with either warping or cracking. Once it comes out of the quench, I give it a quick check for hardness with a file, clean it off, and pop it into the toaster oven for the tempering cycle X 2 for 2 hours each. This consistantly gives me good blades that hold an edge, no warp, and not too much grinding after being hardened.

[toggy]

I see where you are coming from with the 1080.

I am going to start the search for a oil quenchant.

Is it true that A2 can be air-hardened? Might that be a good steel for beginners?

[Ray Rogers]

No, 1080 or 1084 is a good steel for beginners (and the rest of us too). A2 is a good steel for makers who own an electric furnace but, yes, it does air harden - that doesn't mean it doesn't warp though. All steels can warp if they have stresses in them and they all get stressed the same way. Try some 1080, 1084, or even some 1075 or 1065 if you can find them....

[Doug Lester]

The 1095 that The New Jersey Steel Baron sells was formulated with a little higher manganese specifically for knife making. Aldo found an outfit that would make a custom melt for him and he had the money to pay for it. I talked to him about it at a hammer-in about two years ago and he said that they managed to come in real close to specs on it. Admiral is not really a supplier of steel to the cutlery industry but they do carry steels that can be used for knife making and are willing to sell in small quantities. It's just a side line for them. The 1095 that they carry is for manufacturers who don't care all that much about the manganese levels in their steel and when you order from them you get what you get. Some melts will be better than others when it comes to heat treating.

Doug

[toggy]

Ok, that makes sense. I'll be ordering some lower-than-1095 carbon steel from the baron (once I get in the black again)